000			02730nam a2200325Ia 4500
008			220216s9999 xx 000 0 und d
100			_aBouteau F
245		0	_aSucrose/H+ and glucose/H+ symports at the plasma membrane of laticiferous cells and protoplasts of Hevea brasiliensis
260			_bIndian Journal of Natural Rubber Research _c1992
300			_a25-37
520			_aPolyisoprene synthesis in ethylene stimulated laticiferous cells of Hevea brasiliensis requires an exogenous supply of sugar. Plasmodesmata are absent from these non-chlorophyllian cells. The transplasmalemmal electrical gradient recorded at steady state was about-115 mV for laticiferous cells and -36mV for laticiferous protoplasts. Sucrose and glucose depolarize the plasmalemma of laticiferous cells by about 15 to 25 mV and by about 1 to 7 mV laticiferous protoplasts. Results show that with depolarization due to sucrose (1 mM) or glucose (1 mM), a slight alkalinization (0.1 to 0.2 pH units) can be detected on the outer surface of the cell. Fructose and 3-0-methyl-glucose have no such effect. The extent of depolarization due to the addition of sugars is lower than the electrogenic component of the membrane potential produced by the functioning of the H+-excretion pump (vandate sensitive-ATPase). Furthermore, in presence of vanadate or DNP, no shift in pH value was observed with glucose or sucrose. The effect of phlorizin on the shift of the membrane potential due to sugar uptake across the plasmalemma has been tested. Neither sucrose nor glucose demonstrate any depolarization and alkalinization in the presence of phlorizin. Stimulation of the H+-pump by ethylene hyperpolarizes cells by approximately -40mV and increases the extent of the depolarization induced by sugar transport. Even without the cellwall, with laticiferous protoplast, glucose and sucrose induce depolarization of plasmalemma. On these protoplasts, sugars do not induce any depolarization in the presence of DNP. These results suggest an active transport of the sugars from the apoplasm towards the cytosol. Evidence for the existence of H+ cotransport with sucrose and/or glucose at the plasmalemma is discussed.
650			_aEthylene
650			_aEthylene
650			_aHevea brasiliensis
650			_aHevea brasiliensis
650			_aLaticiferous cells
650			_aLaticiferous cells
650			_aLaticiferous protoplasts
650			_aLaticiferous protoplasts
650			_aMembrane potential
650			_aMembrane potential
650			_aPhlorizin
650			_aPhlorizin
700			_aBousquet U
700			_aCornel D
700			_aLacrotte R
700			_aMonestiez M
700			_aRona J P
942			_cAR
999			_c47062 _d47062